Hepacivirus cross-species transmission and the origins of the hepatitis C virus

- Cross-species transmission of equine hepaciviruses to dogs may be recent and direct.
- Rodents and bats are plausible reservoir species of diverse hepaciviruses.
- Origins of the hepatitis C virus are opaque but may involve one or many zoonoses.

Just 5 years ago the hepatitis C virus (HCV) - a major cause of liver disease infecting >3% of people worldwide - was the sole confirmed member of the Hepacivirus genus. Since then, genetically-diverse hepaciviruses have been isolated from bats, dogs, cows, horses, primates and rodents. Here we review current information on the hepaciviruses and speculate on the zoonotic origins of the viruses in humans, horses and dogs. Recent and direct cross-species transmission from horses to dogs appears plausible, but the zoonotic origins of HCV in humans remain opaque. Mechanical transmission by biting insects, notably tabanids, could, in theory, connect all three host species. Much further work is needed to understand the transmission and zoonotic potential of hepaciviruses in natural populations.